High doses of the herb American ginseng (Panax quinquefolius) over two months reduced cancer-related fatigue in patients more effectively than a placebo, a Mayo Clinic-led study found. Sixty percent of patients studied had breast cancer. The findings are being presented at the American Society of Clinical Oncology's annual meeting. Researchers studied 340 patients who had completed cancer treatment or were being treated for cancer at one of 40 community medical centers. Each day, participants received a placebo or 2,000 milligrams of ginseng administered in capsules containing pure, ground American ginseng root.